Solid-state imaging device and radiotion imaging system

ABSTRACT

N + -type semiconductor regions  12   d  are formed on a front surface side of a p − -type layer  12   c  of a semiconductor substrate  12 , and these n + -type semiconductor and p − -type semiconductor constitute photodiodes. A metal wire  14  electrically connected to an isolation region  12   e  is formed on a first insulating layer  13 . The metal wire  14  is provided so that its edge covers pn junction portions (interfaces between p − -type layer  12   c  and n + -type semiconductor regions  12   d ) exposed on a light-incident surface of the semiconductor substrate  12  (p − -type layer  12   c ), above the pn junction portions, and is of grid shape. The metal wire  14  is grounded and the isolation region  12   e  is set at the ground potential.

TECHNICAL FIELD

The present invention relates to a solid-state imaging apparatus and aradiographic imaging apparatus.

BACKGROUND ART

An example of the known radiographic imaging apparatus of this type isone having a fiber optical plate (hereinafter referred to as FOP), ascintillator disposed on one surface of the FOP, and an MOS image sensordisposed opposite to the scintillator on the other surface of the FOP(e.g., reference is made to Patent Document 1).

Another example of the known radiographic imaging apparatus is onehaving a photodetector array in which photodetectors for photoelectricconversion are arrayed in a one-dimensional or two-dimensional pattern,and a scintillator formed directly on light-incident surfaces of thephotodetectors (e.g., reference is made to Patent Document 2).

[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-28735

[Patent Document 2] PCT International Publication WO98/36290

DISCLOSURE OF THE INVENTION

In the case of the imaging apparatus as disclosed in Patent Document 1above, it was impossible to further increase the area of the FOP itselfand it was thus difficult to increase the image detecting area to alarger area. For this reason, one of conceivable countermeasures is thetechnique of forming the scintillator directly on the light-incidentsurfaces of the photodetectors, without use of the FOP, as disclosed inPatent Document 2 above. Another conceivable means is a technique offorming the scintillator on a support and bringing the scintillator intoclose contact with the light-incident surfaces of the photodetectors,instead of forming the scintillator directly on the light-incidentsurfaces of the photodetectors.

However, the configuration without the FOP was found to pose a newproblem of deterioration of SN ratio. Research and study by Inventorshas turned up the following new fact. Where the FOP is present, lead inthe FOP shields against radiation not converted to light by thescintillator. Without the FOP, however, the radiation not converted tolight by the scintillator is directly incident to the MOS image sensorto generate charge in the region except for the photodiodes, e.g., in asurface oxide film (such as a silicon oxide film) being a surfaceprotecting film of the MOS image sensor. The generated charge isaccumulated (or charged up) in a pn junction portion, whereby aninterface leak of charge occurs in the pn junction portion being theedge of a photodiode, to generate a leak current. This leak current issuperimposed on an electric current output from the photodiode todegrade the SN ratio.

An object of the present invention is to provide a solid-state imagingapparatus and a radiographic imaging apparatus capable of suppressingthe occurrence of the interface leak of charge in the pn junctionportion and thereby preventing the deterioration of the SN ratio.

A solid-state imaging apparatus according to the present inventioncomprises: a photosensitive section comprising a semiconductor substrateof a first conductivity type, and a plurality of second conductivitytype semiconductor regions arrayed in a two-dimensional pattern on oneside of the semiconductor substrate, wherein the semiconductor substrateand each second conductivity type semiconductor region constitute a pnjunction to function as a photodiode; and an electroconductive memberprovided so as to cover at least the pn junction portions exposed on theone side of the semiconductor substrate, wherein the electroconductivemember is connected to a fixed potential, or is grounded.

In the solid-state imaging apparatus according to the present invention,the electroconductive member provided so as to cover at least the pnjunction portions exposed on one side of the semiconductor substrate isconnected to the fixed potential, or is grounded, and thus the chargegenerated in the region except for the photodiodes is discharged throughthe electroconductive member to the outside, without being accumulatedin the pn junction portions. For this reason, it is feasible to suppressthe occurrence of the interface leak of charge in the pn junctionportions and thereby prevent the deterioration of the SN ratio.

Preferably, the electroconductive member is of grid shape when viewedfrom a direction of incidence of light to the photosensitive section,and is provided so as to cover the pn junction portions exposed on theone side of the semiconductor substrate and portions between the secondconductivity type semiconductor regions adjacent to each other. Thisconfiguration permits the electroconductive member to be simply andeasily implemented in the configuration capable of discharging thecharge generated in the region except for the photodiodes, to theoutside and thereby surely suppressing the occurrence of the interfaceleak of charge in the pn junction portions.

Preferably, the photosensitive section further comprises an isolationregion formed between the second conductivity type semiconductor regionsadjacent to each other, and the electroconductive member is electricallyconnected to the isolation region. This configuration can achievecommonality between the electroconductive member for discharging thecharge generated in the region except for the photodiodes, to theoutside, and the electroconductive member for connecting the isolationregion to the fixed potential or grounding it, thereby preventingcomplexity of structure.

Preferably, the solid-state imaging apparatus is configured in aconfiguration further comprising: signal lines for readout of outputsfrom the photodiodes, which are electrically connected to thephotodiodes; a switch group consisting of a plurality of switches forcontrolling electrical connection and disconnection between eachphotodiode and the signal line in each column of the photodiodes; andwires connected to control terminals of the respective switches formingthe switch group, and arranged to supply a scan signal to turn eachswitch off or on in each row of the photodiodes, to the controlterminals, wherein the wires are located above the electroconductivemember. In this configuration, the electroconductive member shieldsagainst noise generated with change of supply voltage in the wires onthe occasion of supplying the scan signal to the control terminals. Thiscan prevent the noise from being superimposed on outputs from thephotodiodes.

Another solid-state imaging apparatus according to the present inventioncomprises: a photosensitive section comprising a semiconductor substrateof a first conductivity type, and a plurality of second conductivitytype semiconductor regions arrayed in a matrix of M rows and N columnson one side of the semiconductor substrate, wherein the semiconductorsubstrate and each second conductivity type semiconductor regionconstitute a pn junction to function as a photodiode; first wiresprovided in the respective columns; a fist switch group consisting of aplurality of switches for connection between each photodiode and thefirst wire in each column; a vertical shift register for outputting avertical scan signal to open and close each switch forming the firstswitch group, in each row; second wires for connecting control terminalsof the respective switches forming the first switch group, to thevertical shift register in each row, a second switch group consisting ofa plurality of switches for connection between each first wire and asignal output line; a horizontal shift register for outputting ahorizontal scan signal to open and close each switch forming the secondswitch group, m each column; and an electroconductive member provided soas to cover at least the pn junction portions exposed on the one side ofthe semiconductor substrate, wherein the electroconductive member isconnected to a fixed potential, or is grounded.

Preferably, the second wires are located above the electroconductivemember. In this configuration, the electroconductive member shieldsagainst noise generated with change of supply voltage in the secondwires on the occasion of supplying the scan signal to the controlterminals. This can prevent the noise from being superimposed on outputsfrom the photodiodes.

Still another solid-state imaging apparatus according to the presentinvention comprises: a photosensitive section comprising a semiconductorsubstrate of a first conductivity type, and a plurality of secondconductivity type semiconductor regions arrayed in a two-dimensionalpattern on one side of the semiconductor substrate, wherein thesemiconductor substrate and each second conductivity type semiconductorregion constitute a pn junction to function as a photodiode; and anelectroconductive member for discharging a charge generated in a regionexcept for the photodiodes, to the outside.

In the solid-state imaging apparatus according to the present invention,the charge generated in the region except for the photodiodes isdischarged through the electroconductive member to the outside, withoutbeing accumulated in the pn junction portions. For this reason, it isfeasible to suppress the occurrence of the interface leak of charge inthe pn junction portions and thereby prevent the deterioration of the SNratio.

Preferably, the electroconductive member is provided above the pnjunction portions so as to cover at least the pn junction portionsexposed on the one side of the semiconductor substrate, and is connectedto a fixed potential or is grounded. This configuration permits theelectroconductive member to be simply and easily implemented in theconfiguration capable of discharging the charge generated in the regionexcept for the photodiodes, to the outside.

A radiographic imaging apparatus according to the present inventioncomprises the foregoing solid-state imaging apparatus, and ascintillator for converting radiation to visible light, which isprovided so as to cover the plurality of photodiodes.

In the radiographic imaging apparatus according to the presentinvention, as described above, the charge generated in the region exceptfor the photodiodes is discharged through the electroconductive memberto the outside, without being accumulated in the pn junction portions,whereby it is feasible to suppress the occurrence of the interface leakof charge in the pn junction portions and thereby prevent thedeterioration of the SN ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view for explaining a cross-sectionalconfiguration of a radiographic imaging apparatus according to anembodiment of the present invention.

FIG. 2 is a schematic view for explaining the cross-sectionalconfiguration of the radiographic imaging apparatus according to theembodiment of the present invention.

FIG. 3 is a plan view showing the radiographic imaging apparatusaccording to the embodiment of the present invention.

FIG. 4 is a configuration diagram showing the radiographic imagingapparatus according to the embodiment of the present invention.

FIG. 5 is a plan view showing a photosensitive section included in asolid-state image sensor of the radiographic imaging apparatus accordingto the embodiment of the present invention.

FIG. 6 is a schematic view for explaining a cross-sectionalconfiguration along line VI-VI in FIG. 5.

FIG. 7 is a schematic view for explaining a cross-sectionalconfiguration along line VII-VII in FIG. 5.

FIG. 8 is a schematic view for explaining a cross-sectionalconfiguration along line VIII-VIII in FIG. 5.

FIG. 9 is a schematic view for explaining a cross-sectionalconfiguration along line IX-IX in FIG. 5.

FIG. 10 is a schematic diagram for explaining a cross-sectionalconfiguration of the photosensitive section included in the solid-stateimage sensor in the radiographic imaging apparatus according to theembodiment of the present invention.

FIG. 11 is a schematic diagram for explaining a cross-sectionalconfiguration in a modification example of the radiographic imagingapparatus according to the embodiment of the present invention.

FIG. 12 is a schematic diagram for explaining a cross-sectionalconfiguration in another modification example of the radiographicimaging apparatus according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will be described belowin detail with reference to the drawings. Identical elements or elementswith identical functionality will be denoted by the same referencesymbols in the description, without redundant description. Aradiographic imaging apparatus according to the present embodimentincorporates a solid-state imaging apparatus (solid-state image sensor)according to an embodiment of the present invention.

FIGS. 1 and 2 are schematic views for explaining a cross-sectionalconfiguration of the radiographic imaging apparatus according to thepresent embodiment, and FIG. 3 is a plan view showing the radiographicimaging apparatus according to the present embodiment. FIG. 4 is aconfiguration diagram showing the radiographic imaging apparatusaccording to the present embodiment. FIG. 3 is depicted withoutillustration of bonding wires.

The radiographic imaging apparatus 1 of the present embodiment, as shownin FIGS. 1 to 3, has a solid-state image sensor 11, a scintillator 21, amount substrate 23, a frame 25, and others.

The solid-state image sensor 11 is an MOS image sensor, and has aphotosensitive section 31, a shift register section 41, and anamplification section 51, which are formed on one side of asemiconductor substrate 12. In this manner, the photosensitive section31, the shift register section 41, and the amplification section 51 areformed on the same substrate (semiconductor substrate 12). Thesemiconductor substrate 12 (solid-state image sensor 11) is fixed on themount substrate 23. In the present embodiment, the area of thesemiconductor substrate 12 is approximately 16900 mm²(=130 mm×130 mm),and the area of the photosensitive section 31 approximately 15625mm²(=125 mm×125 mm).

The photosensitive section 31, as shown in FIG. 4, is constructed in aconfiguration wherein a plurality of photodiodes (photoelectricconverters) 33 for storing charges according to intensities of incidentlight are arrayed in a two-dimensional pattern on the semiconductorsubstrate 12. More specifically, the photosensitive section 31 iscomposed of M×N photodiodes 33 arrayed in a matrix of M rows in they-axis direction and N columns in the x-axis direction (M and N arenatural numbers). In FIG. 4, M and N are determined to be “4.”

Each of the photodiodes 33 forming the photosensitive section 31 isprovided with a gate switch (switch forming a first switch group) 35 oneend of which is electrically connected to the photodiode 33 and theother end of which is electrically connected to a signal readout linedescribed later. Therefore, during an opening period of the gate switch35, a charge is stored in the photodiode 33 with incidence of light, andthe charge stored in the photodiode 33 is read out to thelater-described signal readout line with closure of the gate switch 35.The gate switch 35 can be constructed of an MOSFET (field effecttransistor).

The shift register section 41 includes a vertical shift register 43 andis formed so as to face one side of the photosensitive section 31, onthe semiconductor substrate 12. The vertical shift register 43 outputs avertical scan signal to open and close each gate switch 35. The verticalscan signal includes two types of drive voltages at a high (H) level andat a low (L) level, and the difference between these drive voltages isapproximately several V.

A control terminal of each gate switch 35 is electrically connected tothe vertical shift register 43 by a gate line (second wire; wire) 45. Inthis configuration, each gate switch 35 can be opened and closed by avertical scan signal outputted from the vertical shift register 43.Specifically, the gate lines 45 extend in the x-axis direction throughportions between rows of photodiodes 33 arrayed in the photosensitivesection 31, and each gate line 45 is connected to the control terminalsof the respective gate switches 35 existing in one row. Accordingly, thevertical shift register 43 and the control terminals of the gateswitches 35 are connected on a row-by-row basis.

Furthermore, N signal readout lines (first wires; signal lines) 53 towhich the other ends of the gate switches 35 are electrically connectedin each column are provided between columns of photodiodes 33 arrayed inthe photosensitive section 31. The N signal readout lines 53 areelectrically connected to the amplification section 51. Theamplification section 51 includes charge amplifiers 55, readout switches(switches constituting a second switch group) 57, a horizontal shiftregister 59, and so on. The amplification section 51 is formed so as toface one side adjacent to the one side of the photosensitive section 31which the shift register section 41 is formed so as to face, on thesemiconductor substrate 12.

The charge amplifiers 55 are provided for the respective signal readoutlines 53, and amplify charges (electric current outputs), which is readout into the signal readout lines 53. The readout switches 57 areprovided for the respective signal readout lines 53 and output thecharges (electric current outputs), which is read out of the photodiodes33, to a signal output line 60. The horizontal shift register 59 outputsa horizontal scan signal to open and close each readout switch 57.

A plurality of bonding pads 61 electrically connected to the amplifiersection 51 are formed on the semiconductor substrate 12, as shown inFIGS. 2 and 3. These bonding pads 61 are electrically connected tocorresponding bonding pads 65 formed on the mount substrate 23, bybonding wires 63. In this configuration, the outputs from theamplification section 51 are supplied via the mount substrate 23 to theoutside of the imaging apparatus 1. A plurality of bonding pads 67electrically connected to the shift register section 41 are formed onthe semiconductor substrate 12 (particularly, cf FIG. 3). These bondingpads 67 are electrically connected to corresponding bonding pads 69formed on the mount substrate 23, by bonding wires (not shown). In thisconfiguration, signals from the outside of the imaging apparatus 1 aresupplied via the mount substrate 23 to the shift register section 41.

The scintillator 21 converts incident radiation (e.g., X-rays) tovisible light and is of columnar structure. The scintillator 21, as alsoshown in FIG. 3, is arranged to cover the region where thephotosensitive section 31, the shift register section 41, and theamplification section 51 are formed on one side of the semiconductorsubstrate 12, and is formed directly on the region. In thisconfiguration, the scintillator 21 is arranged in contact with theregion where the photosensitive section 31, the shift register section41, and the amplification section 51 are formed on one side of thesemiconductor substrate 12. The region where the bonding pads 61, 67 areformed on one side of the semiconductor substrate 12 is not covered bythe scintillator 21, and is exposed.

A variety of materials can be used for the scintillator 21, and one ofpreferred materials is Tl (thallium) doped CsI, which demonstrates goodluminous efficiency. A protective film (not shown) for hermeticallysealing the scintillator 21 while covering the columnar structure of thescintillator 21 so as to fill its gaps is formed on the scintillator 21.The protective film is preferably a material that transmits radiationbut shields against water vapor, e.g., poly-para-xylylene (trade nameParylene, available from Three Bond Co., Ltd.), and particularlypreferably, poly-para-chloroxylylene (trade name Parylene C, availablefrom the same company). In the present embodiment, the thickness of thescintillator 21 is approximately 300 μm.

The scintillator 21 can be formed by growing columnar crystals of CsI bydeposition method. The protective film can be formed by CVD. The methodsof forming the scintillator 21 and the protective film are disclosed indetail in PCT International Publication WO98/36290 filed by Applicant ofthe present application, for example, and the description thereof isomitted herein.

The frame 25 is fixed on the mount substrate 23 so as to surround thesolid-state image sensor 11. The frame 25 has an opening 27 ofrectangular shape formed at the position corresponding to thephotosensitive section 31, and radiation is incident through the opening27 to the scintillator 21. A space S is created between the frame 25,and the semiconductor substrate 12 and the mount substrate 23. The shiftregister section 41 and the amplification section 51 of the solid-stateimage sensor 11, the bonding pads 61, 65, the bonding wires 63, etc. arelocated inside the space S. Since the bonding wires 63 are placed insidethe space S defined by the frame 25, the semiconductor substrate 12, andthe mount substrate 23 as described above, the bonding wires 63 areprotected from external physical stress, without being pushed by theframe 25. In addition, a shield 29 of a radiation-shielding material(e.g., lead or the like) is provided on the side opposite to theamplification section 51 side, on the frame 25, and the shield 29 wellshields against radiation. In the present embodiment, the thickness ofthe shield 29 is approximately 2.5 mm.

Next the configuration of the photosensitive section 31 will bedescribed on the basis of FIGS. 5 to 9. FIG. 5 is a plan view showingthe photosensitive section. FIG. 6 is a schematic view for explaining across-sectional configuration along line VI-VI in FIG. 5. FIG. 7 is aschematic view for explaining a cross-sectional configuration along lineVII-VII in FIG. 5. FIG. 8 is a schematic view for explaining across-sectional configuration along line VIII-VIII in FIG. 5. FIG. 9 isa schematic view for explaining a cross-sectional configuration alongline IX-IX in FIG. 5. FIG. 5 is depicted without illustration of firstto fourth insulating layers 13, 15-17, and the gate switches 35.

The semiconductor substrate 12, as shown in FIGS. 6 to 9, includes ap⁺-type semiconductor substrate 12 a, and a p⁻-type epitaxialsemiconductor layer 12 b and a p⁻-type layer 12 c are formed on thep⁺-type semiconductor substrate 12 a. The p⁺-type semiconductorsubstrate 12 a is set at the ground potential. The solid-state imagesensor 11 is one using Si as a semiconductor, “high concentration”refers to the impurity concentration of not less than about 1×10¹⁷/cm³and is expressed by “+” attached to the conductivity type; “lowconcentration” refers to the impurity concentration of not more thanabout 1×10¹⁵/cm³ and is expressed by “−” attached to the conductivitytype.

N⁺-type semiconductor regions 12 d are formed on the front surface sideof the p⁻-type layer 12 c, and a pn junction composed of each n⁺-typesemiconductor (n⁺-type semiconductor region 12 d) and the p⁻-typesemiconductor (p⁻-type layer 12 c) constitutes a photodiode(photoelectric converter) 33. The n⁺-type semiconductor regions 12 deach are of rectangular shape when viewed from the direction ofincidence of light, and are arrayed in a two-dimensional pattern of Mrows and N columns, as shown in FIG. 5. In this configuration, thephotodiodes 33 are arrayed in the two-dimensional pattern of M rows andN columns in the photosensitive section 31. In the present embodiment,the length on each side of the n⁺-type semiconductor regions 12 d is setto be approximately 50 μm.

An isolation region 12 e of p⁺-type semiconductor is formed betweenadjacent n⁺-type semiconductor regions 12 d on the front surface side ofthe p⁻-type layer 12 c. The isolation region 12 e, as shown in FIG. 5,extends along the row direction and along the column direction betweenadjacent n⁺-type semiconductor regions 12 d and is of grid shape whenviewed from the direction of incidence of light.

A first insulating layer (e.g., made of a silicon oxide film) 13 isformed on the p⁻-type layer 12 c, the n⁺-type semiconductor regions 12d, and the isolation region 12 e. A metal (e.g., aluminum) wire(electroconductive member) 14 is electrically connected to the isolationregion 12 e via through holes formed in the first insulating layer 13.The metal wire 14, as shown in FIG. 5, is provided so as to extend alongthe row direction and along the column direction between adjacentn⁺-type semiconductor regions 12 d, and is of grid shape when viewedfrom the direction of incidence of light. The metal wire 14 is groundedand thus the isolation region 12 e is set at the ground potential. Themetal wire 14 may also be connected to a fixed potential, instead ofbeing grounded.

The width of the metal wire 14 is set greater than the distance betweenadjacent n⁺-type semiconductor regions 12 d, and part of the metal wire14 overlaps the edges of n⁺-type semiconductor regions 12 d when viewedfrom the direction of incidence of light. Namely, the metal wire 14 isprovided above the pn junction portions so that its edge covers the pnjunction portions (the interfaces between the p⁻-type layer 12 c and then⁺-type semiconductor regions 12 d) exposed on the light-incidentsurface (one side) of the semiconductor substrate 12 (p⁻-type layer 12c).

The metal wire 14, as shown in FIG. 10, is preferably provided so as tocover depletion layers 12 f formed in the pn junction portions (theinterfaces between the p⁻-type layer 12 c and the n⁺-type semiconductorregions 12 d). The size (width) of the depletion layers 12 f isdependent upon an impurity concentration in the p⁻-type layer 12 c, animpurity concentration in the n⁺-type semiconductor region 12 d, anapplied voltage, and so on. For this reason, the width of the metal wire14, i.e., the width of the overlapping part with the n⁺-typesemiconductor regions 12 d in order to cover the pn junction portionsneeds to be set, in consideration of these factors. In the presentembodiment, the distance between adjacent n⁺-type semiconductor regions12 d is approximately 4 μm, and the width of the metal wire 14approximately 5 μm.

A second insulating layer (e.g., made of a silicon oxide film) 15 isformed on the first insulating layer 13. The aforementioned gate lines45 and a third insulating layer (e.g., made of a silicon oxide film) 16are formed on the second insulating layer 15. The gate lines 45 are madeof metal such as aluminum, located above the metal wire 14 when viewedfrom the direction of incidence of light, as shown in FIGS. 5, 7, and 8,and provided so as to extend along the row direction and betweenadjacent n⁺-type semiconductor regions 12 d.

The aforementioned signal readout lines 53 and a fourth insulating layer(e.g., made of a silicon oxide film) 17 are formed on the thirdinsulating layer 16. The signal readout lines 53 are made of metal suchas aluminum, and, as shown in FIGS. 5 and 6, the signal readout lines 53are located above the n⁺-type semiconductor regions 12 d when viewedfrom the direction of incidence of light, and are provided so as toextend along the column direction. In the present embodiment the widthof the signal readout lines 53 is set to be approximately 0.5 μm. Thesignal readout lines 53 are placed with deviation of approximately 1-20μm from one side of n⁺-type semiconductor regions 12 d, above then⁺-type semiconductor regions 12 d.

Since in the present embodiment the metal wire 14 provided so as tocover at least the pn junction portions exposed on one side of thesemiconductor substrate 12 is grounded as described above, the chargegenerated in the region (first insulating layer 13) except for thephotodiodes 33 is discharged through the metal wire 14 to the outside,without being accumulated in the pn junction portions. For this reason,it is feasible to suppress the occurrence of the interface leak ofcharge in the pn junction portions and thereby prevent the deteriorationof the SN ratio.

In the present embodiment, the metal wire 14 is of grid shape whenviewed from the direction of incidence of light to the photosensitivesection 31, and is provided so as to cover the pn junction portionsexposed on one side of the semiconductor substrate 12 and the portionsbetween adjacent n⁺-type semiconductor regions 12 d. This permits theelectroconductive member to be simply and readily implemented in theconfiguration capable of discharging the charge generated in the regionexcept for the photodiodes 33, to the outside and securely suppressingthe occurrence of the interface leak of charge in the pn junctionportions.

In the present embodiment, the photosensitive section 31 includes theisolation region 12 e formed between adjacent n⁺-type semiconductorregions 12 d, and the metal wire 14 is electrically connected to theisolation region 12 e. This can achieve commonality between theelectroconductive member for discharging the charge generated in theregion except for the photodiodes 33, to the outside, and theelectroconductive member for grounding the isolation region 12 e,thereby preventing complexity of structure.

In the present embodiment, the gate lines 45 are located above the metalwire 14. In this configuration, the metal wire 14 shields against thenoise generated with change of the supply voltage (switching between theH level and the L level) in the gate lines 45 on the occasion ofsupplying the vertical scan signal to the control terminal of each gateswitch 35. This can prevent the noise from being superimposed on theoutputs from the photodiodes 33.

The present invention is by no means limited to the above-describedembodiment. The present embodiment is configured to discharge the chargegenerated in the region except for the photodiodes 33 to the outside bythe metal wire 14 for grounding the isolation region 12 e, but theinvention is not limited to this configuration. For example, as shown inFIG. 11, it is also possible to adopt a configuration wherein anelectroconductive member 71 (e.g., an aluminum wire), separate from themetal wire 14 for grounding the isolation region 12 e, is provided so asto cover at least the pn junction portions exposed on one side of thesemiconductor substrate 12 and wherein the charge generated in theregion except for the photodiodes 33 is discharged to the outside by theelectroconductive member 71. It is also possible to adopt anotherconfiguration, as shown in FIG. 12, wherein an electroconductive member73 of polysilicon is provided so as to cover at least the pn junctionportions exposed on one side of the semiconductor substrate 12, in thefirst insulating layer 13 and wherein the charge generated in the regionexcept for the photodiodes 33 is discharged to the outside by theelectroconductive member 73.

The scintillator 21 is formed directly on the semiconductor substrate 12in the present embodiment, but the structure is not limited to this. Forexample, it is also possible to adopt a configuration wherein ascintillator substrate is formed by laying a scintillator on aradiation-transmitting substrate and wherein the scintillator substrateis arranged so as to keep the scintillator in contact with the regionwhere the photosensitive section 31, the shift register section 41, andthe amplification section 51 are formed on one side of the semiconductorsubstrate 12. In a case where a protective film is formed on thescintillator, the protective film is brought into contact with theregion where the photosensitive section 31, the shift register section41, and the amplification section 51 are formed.

INDUSTRIAL APPLICABILITY

The solid-state imaging apparatus and the radiographic imaging apparatusof the present invention are applicable to radiographic imaging systemsof large area, particularly, used in medical and industrial X-rayphotography.

1. A solid-state imaging apparatus comprising: a photosensitive sectioncomprising a semiconductor substrate of a first conductivity type, and aplurality of second conductivity type semiconductor regions arrayed in atwo-dimensional pattern on one side of the semiconductor substrate,wherein the semiconductor substrate and each second conductivity typesemiconductor region constitute a pn junction to function as aphotodiode; signal lines for readout of outputs from the photodiodes,which are electrically connected to the photodiodes; a switch groupconsisting of a plurality of switches for controlling electricalconnection and disconnection between each photodiode and the signal linein each column of the photodiodes; wires connected to control terminalsof the respective switches forming the switch group, and arranged tosupply a scan signal to turn each switch off or on in each row of thephotodiodes, to the control terminals; and an electroconductive memberprovided so as to cover at least the pn junction portions exposed on theone side of the semiconductor substrate, wherein the electroconductivemember is connected to a fixed potential, or is grounded, and whereinthe wires are located above the electroconductive member so as tooverlap the electroconductive member when viewed from a direction ofincidence of light.
 2. The solid-state imaging apparatus according toclaim 1, wherein the electroconductive member is of grid shape whenviewed from a direction of incidence of light to the photosensitivesection, and is provided so as to cover the pn junction portions exposedon the one side of the semiconductor substrate and portions between thesecond conductivity type semiconductor regions adjacent to each other.3. The solid-state imaging apparatus according to claim 1, wherein thephotosensitive section further comprises an isolation region formedbetween the second conductivity type semiconductor regions adjacent toeach other, and wherein the electroconductive member is electricallyconnected to the isolation region.
 4. A radiographic imaging apparatuscomprising: the solid-state imaging apparatus as set forth in claim 1;and a scintillator for converting radiation to visible light, which isprovided so as to cover the plurality of photodiodes and be in contactwith a light incident surface of the solid-state imaging apparatus. 5.The solid-state imaging apparatus according to claim 1, wherein thesignal lines are located above the wires so as to place an insulatinglayer therebetween.
 6. The solid-state imaging apparatus according toclaim 1, wherein the signal lines are located above the secondconductivity type semiconductor regions so as to be apart from portionsbetween the second conductivity type semiconductor regions adjacent toeach other and intersect with the second conductivity type semiconductorregions when viewed from the direction of incidence of light.
 7. Asolid-state imaging apparatus comprising: a photosensitive sectioncomprising a semiconductor substrate of a first conductivity type, and aplurality of second conductivity type semiconductor regions arrayed in amatrix of M rows and N columns on one side of the semiconductorsubstrate, wherein the semiconductor substrate and each secondconductivity type semiconductor region constitute a pn junction tofunction as a photodiode; first wires provided in the respectivecolumns; a first switch group consisting of a plurality of switches forconnection between each photodiode and the first wire in each column; avertical shift register for outputting a vertical scan signal to openand close each switch forming the first switch group, in each row;second wires for connecting control terminals of the respective switchesforming the first switch group, to the vertical shift register in eachrow; a second switch group consisting of a plurality of switches forconnection between each first wire and a signal output line; ahorizontal shift register for outputting a horizontal scan signal toopen and close each switch forming the second switch group, in eachcolumn; and an electroconductive member provided so as to cover at leastthe pn junction portions exposed on the one side of the semiconductorsubstrate, wherein the electroconductive member is connected to a fixedpotential, or is grounded, and wherein the second wires are locatedabove the electroconductive member so as to overlap theelectroconductive member when viewed from a direction of incidence oflight.
 8. The solid-state imaging apparatus according to claim 7,wherein the electroconductive member is of grid shape when viewed from adirection of incidence of light to the photosensitive section, and isprovided so as to cover the pn junction portions exposed on the one sideof the semiconductor substrate and portions between the secondconductivity type semiconductor regions adjacent to each other.
 9. Thesolid-state imaging apparatus according to claim 7, wherein thephotosensitive section further comprises an isolation region formedbetween the second conductivity type semiconductor regions adjacent toeach other, and wherein the electroconductive member is electricallyconnected to the isolation region.
 10. The solid-state imaging apparatusaccording to claim 7, wherein the first wires are located above thesecond wires so as to place an insulating layer therebetween.
 11. Thesolid-state imaging apparatus according to claim 7, wherein the firstwires are located above the second conductivity type semiconductorregions so as to be apart from portions between the second conductivitytype semiconductor regions adjacent to each other and intersect with thesecond conductivity type semiconductor regions when viewed from thedirection of incidence of light.
 12. A radiographic imaging apparatuscomprising: the solid-state imaging apparatus as set forth in claim 7,and a scintillator for converting radiation to visible light, which isprovided so as to cover the plurality of photodiodes and be in contactwith a light incident surface of the solid-state imaging apparatus.